Vacuum cleaners are known, both for domestic and industrial use, in which an internal tank is provided, typically removable from the body of the appliance and having a substantially horizontal flat bottom, for receiving the flow of air sucked up from the outside, with collected dirt and debris mixed therewith.
According to a first technique, known as wet filtration, the tank is loaded with a water volume that fills a portion of limited height and the flow of sucked up air is bubbled through this water volume to cause the release of collected debris and remove fine particulate matter.
The air emerging from the water volume flows back to the outside environment through a special path, and possibly flows therein over the motor of the appliance for cooling it and through a fine-mesh filter for removing any fine particulate residues.
A vacuum cleaner appliance is also known which comprises a dynamic dust removal unit, which is mounted in the tank containing the water volume.
This dynamic dust removal unit comprises a rotatably motor-driven fan which is mounted to the tank ceiling.
The fan has a large number of blades, with passages for the sucked up air therebetween, communicating with a pipe for collecting air and conveying it to the outside.
The fan is driven by a motor whereby it provides the sucking action, by creating a negative pressure in the tank.
The air emerging from the water volume after bubbling and release of debris and fine particulate matter is sucked up through the passages defined between the blades and any residual suspended dirt particles or debris are separated from the air flow by direct impact against the blades of the rotating fan.
The particles rejected by the blades fall back into the water volume with those collected during bubbling, for disposal when the water volume is heavily loaded with dirt and is emptied from the tank and replaced with a new clean water volume.
According to another technique, known as dry filtration, vacuum cleaners are known in which the debris and dirt collection tank uses no water but only one or more filters mounted in the tank or directly to the motor that generates the suction force, which filters separate the debris and the particulate matter from the flow of sucked up air prior to reintroduction thereof into the environment after purification.
While these known appliances have an adequate operation, they still suffer from certain drawbacks.
A first drawback is that each vacuum cleaner appliance is manufactured and commercially available in one of the above described versions only.
Therefore, in order that a user can purify the sucked up air prior to reintroduction thereof into the environment using wet filtration, by simple bubbling in water or by dynamic dust removal, or using dry filtration, he/she should buy three distinct appliances, or select one of them and give up the others.
A further drawback of prior art appliances is that the bottom of the compartment in which the sucked up dirt is collected is substantially flat and parallel to the ground, whereby the solid debris sucked up and separated from the air flow are collected on the bottom in random fashion, and no spontaneous accumulation area is provided, for such debris to be quickly picked up and discharged without repeatedly removing the tank from the suction cleaner when small amounts of collected debris and particulate matter are present.